Fix buggy behavior of the "Add tab" button in the scene tabs

2 files changed, 41 insertions, 30 deletions

diff --git a/editor/editor_node.cpp b/editor/editor_node.cpp
index deafe65baf..f30a790322 100644
--- a/editor/editor_node.cpp
+++ b/editor/editor_node.cpp
@@ -312,7 +312,7 @@ void EditorNode::_update_scene_tabs() {
 		DisplayServer::get_singleton()->global_menu_clear("_dock");
 	}
 
-	// Get all scene names, which may be ambiguous
+	// Get all scene names, which may be ambiguous.
 	Vector<String> disambiguated_scene_names;
 	Vector<String> full_path_names;
 	for (int i = 0; i < editor_data.get_edited_scene_count(); i++) {
@@ -349,34 +349,35 @@ void EditorNode::_update_scene_tabs() {
 		DisplayServer::get_singleton()->global_menu_add_item("_dock", TTR("New Window"), callable_mp(this, &EditorNode::_global_menu_new_window));
 	}
 
-	scene_tabs->set_current_tab(editor_data.get_edited_scene());
+	if (scene_tabs->get_tab_count() > 0) {
+		scene_tabs->set_current_tab(editor_data.get_edited_scene());
+	}
 
 	if (scene_tabs->get_offset_buttons_visible()) {
-		// move add button to fixed position on the tabbar
+		// Move the add button to a fixed position.
 		if (scene_tab_add->get_parent() == scene_tabs) {
-			if (scene_tabs->is_layout_rtl()) {
-				scene_tab_add->set_position(Point2(tabbar_container->get_size().x - scene_tab_add->get_size().x, 0));
-			} else {
-				scene_tab_add->set_position(Point2(0, 0));
-			}
 			scene_tabs->remove_child(scene_tab_add);
-			tabbar_container->add_child(scene_tab_add);
-			tabbar_container->move_child(scene_tab_add, 1);
+			scene_tab_add_ph->add_child(scene_tab_add);
+			scene_tab_add->set_position(Point2());
 		}
 	} else {
-		// move add button to after last tab
-		if (scene_tab_add->get_parent() == tabbar_container) {
-			tabbar_container->remove_child(scene_tab_add);
+		// Move the add button to be after the last tab.
+		if (scene_tab_add->get_parent() == scene_tab_add_ph) {
+			scene_tab_add_ph->remove_child(scene_tab_add);
 			scene_tabs->add_child(scene_tab_add);
 		}
-		Rect2 last_tab = Rect2();
-		if (scene_tabs->get_tab_count() != 0) {
-			last_tab = scene_tabs->get_tab_rect(scene_tabs->get_tab_count() - 1);
+
+		if (scene_tabs->get_tab_count() == 0) {
+			scene_tab_add->set_position(Point2());
+			return;
 		}
+
+		Rect2 last_tab = scene_tabs->get_tab_rect(scene_tabs->get_tab_count() - 1);
+		int hsep = scene_tabs->get_theme_constant(SNAME("hseparation"));
 		if (scene_tabs->is_layout_rtl()) {
-			scene_tab_add->set_position(Point2(last_tab.get_position().x - scene_tab_add->get_size().x - 3, last_tab.get_position().y));
+			scene_tab_add->set_position(Point2(last_tab.position.x - scene_tab_add->get_size().x - hsep, last_tab.position.y));
 		} else {
-			scene_tab_add->set_position(Point2(last_tab.get_position().x + last_tab.get_size().x + 3, last_tab.get_position().y));
+			scene_tab_add->set_position(Point2(last_tab.position.x + last_tab.size.width + hsep, last_tab.position.y));
 		}
 	}
 }
@@ -624,6 +625,10 @@ void EditorNode::_notification(int p_what) {
 			editor_data.clear_edited_scenes();
 		} break;
 
+		case Control::NOTIFICATION_THEME_CHANGED: {
+			scene_tab_add_ph->set_custom_minimum_size(scene_tab_add->get_minimum_size());
+		} break;
+
 		case NOTIFICATION_READY: {
 			{
 				_initializing_addons = true;
@@ -6227,6 +6232,9 @@ EditorNode::EditorNode() {
 	tab_preview->set_position(Point2(2, 2) * EDSCALE);
 	tab_preview_panel->add_child(tab_preview);
 
+	tabbar_container = memnew(HBoxContainer);
+	srt->add_child(tabbar_container);
+
 	scene_tabs = memnew(TabBar);
 	scene_tabs->add_theme_style_override("tab_selected", gui_base->get_theme_stylebox(SNAME("SceneTabFG"), SNAME("EditorStyles")));
 	scene_tabs->add_theme_style_override("tab_unselected", gui_base->get_theme_stylebox(SNAME("SceneTabBG"), SNAME("EditorStyles")));
@@ -6244,16 +6252,26 @@ EditorNode::EditorNode() {
 	scene_tabs->connect("gui_input", callable_mp(this, &EditorNode::_scene_tab_input));
 	scene_tabs->connect("active_tab_rearranged", callable_mp(this, &EditorNode::_reposition_active_tab));
 	scene_tabs->connect("resized", callable_mp(this, &EditorNode::_update_scene_tabs));
-
-	tabbar_container = memnew(HBoxContainer);
 	scene_tabs->set_h_size_flags(Control::SIZE_EXPAND_FILL);
+	tabbar_container->add_child(scene_tabs);
 
 	scene_tabs_context_menu = memnew(PopupMenu);
 	tabbar_container->add_child(scene_tabs_context_menu);
 	scene_tabs_context_menu->connect("id_pressed", callable_mp(this, &EditorNode::_menu_option));
 
-	srt->add_child(tabbar_container);
-	tabbar_container->add_child(scene_tabs);
+	scene_tab_add = memnew(Button);
+	scene_tab_add->set_flat(true);
+	scene_tab_add->set_tooltip(TTR("Add a new scene."));
+	scene_tab_add->set_icon(gui_base->get_theme_icon(SNAME("Add"), SNAME("EditorIcons")));
+	scene_tab_add->add_theme_color_override("icon_normal_color", Color(0.6f, 0.6f, 0.6f, 0.8f));
+	scene_tabs->add_child(scene_tab_add);
+	scene_tab_add->connect("pressed", callable_mp(this, &EditorNode::_menu_option), make_binds(FILE_NEW_SCENE));
+
+	scene_tab_add_ph = memnew(Control);
+	scene_tab_add_ph->set_mouse_filter(Control::MOUSE_FILTER_IGNORE);
+	scene_tab_add_ph->set_custom_minimum_size(scene_tab_add->get_minimum_size());
+	tabbar_container->add_child(scene_tab_add_ph);
+
 	distraction_free = memnew(Button);
 	distraction_free->set_flat(true);
 	ED_SHORTCUT_AND_COMMAND("editor/distraction_free_mode", TTR("Distraction Free Mode"), KeyModifierMask::CMD | KeyModifierMask::SHIFT | Key::F11);
@@ -6263,15 +6281,7 @@ EditorNode::EditorNode() {
 	distraction_free->connect("pressed", callable_mp(this, &EditorNode::_toggle_distraction_free_mode));
 	distraction_free->set_icon(gui_base->get_theme_icon(SNAME("DistractionFree"), SNAME("EditorIcons")));
 	distraction_free->set_toggle_mode(true);
-
-	scene_tab_add = memnew(Button);
-	scene_tab_add->set_flat(true);
-	tabbar_container->add_child(scene_tab_add);
 	tabbar_container->add_child(distraction_free);
-	scene_tab_add->set_tooltip(TTR("Add a new scene."));
-	scene_tab_add->set_icon(gui_base->get_theme_icon(SNAME("Add"), SNAME("EditorIcons")));
-	scene_tab_add->add_theme_color_override("icon_normal_color", Color(0.6f, 0.6f, 0.6f, 0.8f));
-	scene_tab_add->connect("pressed", callable_mp(this, &EditorNode::_menu_option), make_binds(FILE_NEW_SCENE));
 
 	scene_root_parent = memnew(PanelContainer);
 	scene_root_parent->set_custom_minimum_size(Size2(0, 80) * EDSCALE);
diff --git a/editor/editor_node.h b/editor/editor_node.h
index f8489777bd..ed6ff3f328 100644
--- a/editor/editor_node.h
+++ b/editor/editor_node.h
@@ -384,6 +384,7 @@ private:
 	HBoxContainer *tabbar_container;
 	Button *distraction_free;
 	Button *scene_tab_add;
+	Control *scene_tab_add_ph;
 
 	bool scene_distraction;
 	bool script_distraction;